#define _CRT_SECURE_NO_WARNINGS 1
#include <iostream>
#include <string>
class Solution {
public:
    string addStrings(string num1, string num2) {
        int end1 = num1.size() - 1;
        int end2 = num2.size() - 1;
        int next = 0;
        int ret = 0;
        string sun;
        while (end1 >= 0 || end2 >= 0)
        {
            int val1 = end1 >= 0 ? num1[end1--] - '0' : 0;
            int val2 = end2 >= 0 ? num2[end2--] - '0' : 0;
            ret = val1 + val2 + next;
            next = ret / 10;
            ret = ret % 10;
            sun += (ret + '0');
        }
        if (next == 1)
            sun += '1';
        reverse(sun.begin(), sun.end());
        return sun;
    }
};